Study of Microcrystalline, Silicon-Carbon p-Layers Prepared by Photo-CVD (Chemical/Vapor Deposition) and Glow Discharge: Final Subcontract Report, December 1, 1987-November 30, 1988.

摘要

Preparation conditions were established for microcrystalline silicon (uc-Si:H) p-type films deposited by both mercury-sensitized photochemical vapor deposition and rf glow discharge. The degree of microcrystallinity in individual films was evaluated in terms of the dark conductivity and optical absorption. Both deposition methods have produced uc-Si: p-layers with conductivities as high as 0.5 S/cm, and optical band gaps between 2.0 and 2.4 eV. For the deposition of such films on glass, a strong decrease of the conductivity below thicknesses of about 100 nm is observed, which is associated with a percolation threshold for conduction. Based on this observation, relatively thick microcrystalline p-layers were incorporated into p-i-n structures. The effect of microcrystallinity is demonstrated by an improvement in the open-circuit voltage, whereas a reduction of the short-circuit current is accounted for by a decrease in the blue-response, due to the excessive absorbance of the relatively thick microcrystalline p-layer. Efficiency improvements require microcrystalline p-layers of lower absorbance, and/or higher conductivity of thinner layers, provided substantial barrier formation at the conductive-transparent-oxide/p-layer interface can be avoided. 15 refs., 8 figs., 5 tabs.